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Certain combinations of permissions can produce significant capability increases and should not be granted. Other permissions should be granted only to special code.

AllPermission

The permission java.security.AllPermission class grants all possible permissions to the callercode. This facility was included for routine testing purposes to make it less cumbersome to deal with to reduce the burden of managing a multitude of permissions or for use when the during routine testing as well as when a body of code is completely trusted. It should never be applied to untrusted code.

Noncompliant Code Example

Code is typically granted AllPermission via the security policy file; it is also possible to programmatically associate AllPermission with a ProtectionDomain. This permission is dangerous in production environments. Never grant AllPermission to untrusted code.

ReflectPermission, suppressAccessChecks

Granting ReflectPermission on the target suppressAccessChecks suppresses all standard Java language access checks when the permitted class attempts to operate on package-private, protected, or private members of another class. Consequently, the permitted class can obtain permissions to examine any field or invoke any method belonging to an arbitrary class [Reflect 2006]. As a result, ReflectPermission must never be granted with target suppressAccessChecks.

According to the technical note Permissions in the Java SE 6 Development Kit [Permissions 2008], Section ReflectPermission, target suppressAccessChecks:

Warning: Extreme caution should be taken before granting this permission to code, for it provides the ability to access fields and invoke methods in a class. This includes not only public, but protected and private fields and methods as well.

RuntimePermission, createClassLoader

The permission java.lang.RuntimePermission applied to target createClassLoader grants code the permission to create a ClassLoader object. This permission is extremely dangerous because malicious code can create its own custom class loader and load classes by assigning them arbitrary permissions. A custom class loader can define a class (or ProtectionDomain) with permissions that override any restrictions specified in the systemwide security policy file.

Permissions in the Java SE 6 Development Kit [Permissions 2008] states:

This is an extremely dangerous permission to grant. Malicious applications that can instantiate their own class loaders could then load their own rogue classes into the system. These newly loaded classes could be placed into any protection domain by the class loader, thereby automatically granting the classes the permissions for that domain.

Noncompliant Code Example (Security Policy File)

This noncompliant example grants AllPermission to the klib library:This noncompliant example grants AllPermission to a library (klib). The permission itself is specified in the security policy file used by the security manager. Alternatively, a permission object can be obtained in the code by subclassing the Permission class (or any subclass like BasicPermission) in the java.security package.

//* grantGrant the klib library AllPermission */ 
grant codebase "file:${klib.home}/j2eej2se/home/klib.jar" { 
  permission java.security.AllPermission; 
}; 

The permission itself is specified in the security policy file used by the security manager. Program code can obtain a permission object by subclassing the java.security.Permission class or any of its subclasses (BasicPermission, for example). The code can use the resulting object to grant AllPermission to a ProtectionDomain.

Compliant Solution

The This compliant solution shows a policy file that can be signed and made to provide more restrictive permissions.used to enforce fine-grained permissions:

grant codeBase 
    "file:${klib.home}/j2eej2se/home/klib.jar", signedBy "Admin" {
    permission java.io.FilePermission "/tmp/*", "read";
    permission java.io.SocketPermission "*", "connect";
};

Always assign appropriate permissions to code. This can be achieved by extending any of the permission classes. The solution below shows how to implement restrictive permissions within the code.To check whether the caller has the requisite permissions, standard Java APIs use code such as the following:

//security Security manager codecheck
FilePermission perm =
    new java.io.FilePermission("/tmp/JavaFile", "read");
AccessController.checkPermission(perm);
//other code

Exceptions

 ...

Always assign appropriate permissions to code. Define custom permissions when the granularity of the standard permissions is insufficient.

Noncompliant Code Example (PermissionCollection)

This noncompliant code example shows an overridden getPermissions() method, defined in a custom class loader. It grants java.lang.ReflectPermission with target suppressAccessChecks to any class that it loads.

protected PermissionCollection getPermissions(CodeSource cs) {
  PermissionCollection pc = super.getPermissions(cs);
  pc.add(new ReflectPermission("suppressAccessChecks"));   // Permission to create a class loader
  // Other permissions
  return pc;
}

Compliant Solution

This compliant solution does not grant java.lang.ReflectPermission with target suppressAccessChecks to any class that it loads:

protected PermissionCollection getPermissions(CodeSource cs) {
  PermissionCollection pc = super.getPermissions(cs);
  // Other permissions
  return pc;
}

Exceptions

ENV03-J-EX0SEC31-EX1: It may be necessary to grant AllPermission to trusted library code so that callbacks will work as expected. For example, it is common practice, and acceptable, to grant AllPermission to the Java system codeoptional Java packages (extension libraries):

// Standard extensions get extend the core platform and are granted all permissions by default

grant codeBase "file:${{java.ext.dirs}}/*" {
	  permission java.security.AllPermission;
};

Risk Assessment

Granting AllPermission to to untrusted code means that there is no security at all allows it to perform privileged operations.

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

\[[API 06|AA. Java References#API 06]\] [Class AllPermission|http://java.sun.com/javase/6/docs/api/java/security/AllPermission.html]
\[[Gong 03|AA. Java References#Gong 03]\]
\[[Security 06|AA. Java References#Security 06]\] [Security Architecture|http://java.sun.com/javase/6/docs/technotes/guides/security/spec/security-spec.doc.html]

Static detection of potential uses of dangerous permissions is a trivial search. Automated determination of the correctness of such uses is not feasible.

Related Vulnerabilities

CVE-2007-5342 describes a vulnerability in Apache Tomcat 5.5.9 through 5.5.25 and 6.0.0 through 6.0.15. The security policy used in the JULI logging component failed to restrict certain permissions for web applications. An attacker could modify the log level, directory, or prefix attributes in the org.apache.juli.FileHandler handler, permitting them to modify logging configuration options and overwrite arbitrary files.

Related Guidelines

Android Implementation Details

The java.security package exists on Android for compatibility purposes only, and it should not be used. Android uses another permission mechanism for security purposes.

Bibliography

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Image Added Image Added Image AddedSEC30-J. Always use a Security Manager      00. Security (SEC)      SEC32-J. Do not grant ReflectPermission with action suppressAccessChecks